Technical Field
The present invention relates generally to lighting control. More particularly, the invention relates to devices, systems, software, and methods for control of light emitting diodes (LEDs).
Background Art
Increasingly, light emitting diodes (LEDs) are providing lighting to commercial and residential structures. These LED lamps and fixtures provide many benefits over conventional lighting technologies, such as higher efficiency, increased lifetime, and relatively safer materials.
An LED driver is an electrical device that regulates power to the LED. LED drivers receive line voltages and convert them to the low voltages typically required by LEDs. There are many types of LED drivers. LED drivers may be internal or external to the LED lamp or fixture and may supply either a constant voltage or a constant current to the lamp or fixture. Certain drivers allow dimming of LEDs, thereby providing a range of lighting levels as well as energy saving opportunities and increased lifetime of the LED.
Traditional phase controlled two-wire LED drivers receive a phase controlled dimmed signal from a dimmer and dim the LED lamps using a dimming scheme based on inhibiting the LED power supply. The lower incoming root mean square (RMS) power is used as raw power delivery that is directly translated to the outbound power delivered into the LED element. In other implementations, a pulse width modulation (PWM) circuitry is included at the front end of the LED driver that applies pulse width modulation directly to the incoming phase controlled dimmed signal and feeds that to the LED element. These implementations, while inexpensive, create several problems.
The power delivered into the LED element is inconsistent causing inconsistent light output and dimming levels. At very low dimming levels, this inconsistency will cause the power supply of the LED driver to sometimes turn on, and at other times turn off. If the power supply is turned off, there will be a period of time where the light will be visibly out. This may cause the LEDs to experience undesired behaviors, such as perceivable flickering or even “dropout” periods. The LEDs may also “pop on” because of this power supply design. Additionally, the LEDs may be at their max brightness well before full power is delivered to them.
Further, dimming LEDs in this manner causes a non-linear relationship between intended brightness and actual LED lumen output. Particularly, in practice the incoming phase controlled dimmed signal is not a perfect sine wave. The wave line suffers from noise that may cause significant fluctuation in voltage levels. At very low dimming levels, and thereby low voltage levels, the noise may cause the LED to turn on at a much lower voltage level than intended. This scheme also produces instability back towards zero cross circuitry. The noise may cause the wave to cross zero voltage at multiple points. In determining the zero cross, the wrong zero cross point may be used, causing a shift in the time cycle. Even a small shift may cause instability in dimming levels, resulting in unwanted flickering.
Accordingly, there is now a need for improved drivers of LED lamps.
Additionally, replacement or reprogramming of constant current LED controls is inconvenient due to configuration requirements. Constant current LED drivers need to be tailored specifically to the LED element to which they are attached. This configuration is typically done one of three ways. LED drivers may be factory configured by ordering them specifically with their current rating. LED drivers may be software programmable at the fixture manufacturer. Lastly, a resistor may be placed on a set of jumpers to configure the current levels.
There is also an issue of LED driver failures in the field. Digital Addressable Lighting Interface (DALI) LED drivers (and ballasts) are soft-addressed, which means that replacement necessitates a commissioning agent to readdress the new device. This is inconvenient and costly to users.
Therefore, there is now a need for improved configuration of LED drivers.